Micro Hydroelectric Penstock Design Analysis PublicDeposited

Quantitative analysis of re-routing a high-head, low-flow, run-of-the-river, under-100 kW hydro electric power plant penstock and comparison with the original route for purposes of head loss estimation and available power prediction.

Descriptions

The infrastructure of a destroyed saw mill is being re-engineered. One project involves installing a micro hydroelectric power station at the end of an existing pipeline. The hydraulic power available to the generator was estimated. Much construction and engineering work has gone into the design and partial build of this power station, including the repair of a pipeline, re-routing the lower pipeline section, and building a bridge. This project focuses on the pipeline that brings water to the power station.
When supplying water to a power station, a pipeline is sometimes called a penstock. In this case, the penstock travels 4 miles underground to bring water from a creek to the power station. There are two possible penstock routes: the old route which comes straight from the creek to the burned mill complex where it zigzags below the ruins through many fittings before reaching the turbine house; and the new route which splices into the old pipeline just before the mill complex and takes a direct path over a bridge to the turbine house. At this point, both pipeline routes are nearly operational and their respective paths were accurately mapped. To assist with turbine and generator selection, an estimate for available hydraulic power was made.
Estimating hydraulic power involves calculating the theoretical maximum power available from the water flowing through a perfect penstock, then subtracting the power lost due to friction, pipeline geometry, and fittings. This was done for several different flow rates. The annual flow variations in the head source creek were also accounted for to ascertain whether sufficient power would be available during the dry fall months. Local protected fish species and their susceptibility to injury by the power station were also noted. The 2001 flow measurements were used as a rough reference.
Pipeline mapping was done using archival maps, GPS, Google, a skydiving altimeter, and static penstock pressure readings. Fittings were counted – with assistance from the map archive – by re-tracing the penstock route above ground and counting the protruding structures. Several old timers, who worked on the pipeline back in the day and still live in the area, were solicited for help during this stage. Pipe material and dimensions was accounted for in much the same way.
Head loss and available power predictions at several flow rates were calculated via two methods: Darcy-Weisbach and Hazen-Williams. Discrepancies between the two methods were noted and discussed. The final results were compared to the 2001 flow measurements and a preliminary turbine selection was made. Future testing was planned.